The present invention relates to a throttle body for an internal combustion engine forming part of an air passage of an internal combustion engine (hereinafter, referred to as engine) and its manufacturing method.
From recent requirements of weight reduction as well as cost reduction, some of conventional engines install a throttle body whose housing is made of a resin.
When the engine is operated in cold districts, a throttle body controlling an intake air amount of the engine is often subjected to icing phenomenon according to which a valve member (i.e., a throttle valve) is frozen together with an inside wall of an intake passage formed in the throttle body under low-temperature conditions.
To prevent the icing phenomenon of the throttle body, it is conventionally known to provide a hot water conduit supplying hot engine cooling water to the vicinity or surrounding of a throttle valve.
FIG. 6 shows a conventional throttle apparatus which discloses a hot water conduit directly formed in the throttle body to guide the hot engine cooling water to the vicinity or surrounding of a throttle valve.
More specifically, as shown in FIG. 6, a throttle body 1 has an intake passage 2 formed therein. A shaft 3 securely fixing a throttle valve 4 is rotatably supported in the housing 1. The throttle valve 4 adjusts an opening degree of the intake passage 2. A hot water conduit 6, which supplies hot engine cooling water, extends straight in the vicinity of the intake passage 2. An inlet pipe 7 and an outlet pipe 8 are connected to an inlet side and an outlet side of this hot water conduit 6. The housing 1 is made of an aluminum member and therefore has relatively better heat-transfer properties. Thus, when the hot engine cooling water flows in the hot water conduit 6, heat of the hot water is transferred to the throttle valve 4.
As described above, when a throttle valve body has an aluminum housing, supplying hot engine cooling water into the hot water conduit formed in the throttle body makes it possible to effectively prevent the throttle valve from icing during a vehicle running condition in cold districts.
However, changing the housing material from aluminum to a resin will cause the following problems.
The heat conductivity of a resin is lower than that of aluminum. It is now assumed that the aluminum housing of the above-described conventional throttle body is simply replaced by a resinous or resin-made housing without changing the arrangement of the hot water conduit. In this case, a sufficient amount of heat will not be transferred to the intake passage side due to low heat conductivity of a resin even if hot water is sufficiently supplied into the hot water conduit.
Unexamined Japanese patent publication 8-135506 discloses a throttle body for an engine which has a resinous or resin-made housing separable into two parts and has a hollow space in the vicinity of an intake passage for introducing hot water.
However, according to the throttle body disclosed in unexamined Japanese patent publication 8-135506, it is necessary to prepare two separate parts for the housing and also necessary to assemble these parts to accomplish the housing. Accordingly, the assembling steps will be complicate and the manufacturing cost increases correspondingly.
Furthermore, according to the throttle body equipped with the aluminum housing 1 shown in FIG. 6, hot engine cooling water is introduced into the hot water conduit 6 locally provided in the throttle body. Therefore, heat of the hot water can be transferred to a limited area of the housing closer to this hot water conduit 6. In other words, insufficient heat is transferred to an opposed side of the housing which is far from the hot water conduit 6 over the throttle valve 4. Accordingly, heat of hot water is not delivered uniformly to the entire area of the housing. This makes it difficult to ensure the anti-icing effect of supplying hot water to the vicinity of the throttle valve. Furthermore, it is necessary to cut the housing partly to form the hot water conduit 6. This will further complicate the manufacturing steps and increase the manufacturing cost.
On the other hand, according to another conventional throttle apparatus, a metallic ring surrounding the outer periphery of a throttle valve is attached to the inside wall of an intake passage of a resinous or resin-made throttle body. Hot water or comparable heating medium is supplied to this metallic ring so as to prevent the icing phenomenon.
However, forming a fluid passage of hot water between an outer wall of the metallic ring and the resinous throttle body is disadvantageous in that hot water may leak between a clearance or gap between the metallic ring and the resinous throttle body. It is usual that the metallic ring is integrally formed with the resinous main body by insert molding. Therefore, sealing the clearance or gap between the metallic ring and the resinous throttle body is very difficult.
According to a throttle apparatus disclosed in the unexamined Japanese utility model publication 4-119352, a recessed groove is formed on an outer wall of a metallic ring so that a fluid pipe of hot water can be engagedly coupled in this recessed groove. This arrangement is effective to prevent hot water from leaking through a clearance or gap between the metallic ring and the resinous throttle body. However, a substantial contact area between the recessed groove and the fluid pipe is dependent on an actual coupling condition between them. It is generally difficult to bring the fluid pipe into complete or satisfactory surface contact with the recessed groove. Thus, an actual contact area between the recessed groove and the fluid pipe is fairly small. The heat of hot water cannot be sufficiently transferred to the metallic ring.
In view of the foregoing problems of the prior art, the present invention has an object to provide a throttle body for an engine which is simple in arrangement and is capable of effectively avoiding the icing phenomenon.
Furthermore, the present invention has another object to provide a method for manufacturing an engine throttle body which is easy to manufacture and is capable of reducing the manufacturing cost.
To accomplish the above and other related objects, a first aspect of the present invention provides a first throttle body for an engine and a first manufacturing method for the engine throttle body. According to the first aspect of the present invention, an inner cylinder and an outer cylinder are formed integrally so that the outer cylinder is disposed outside the inner cylinder. A heating medium passage is formed between the inner cylinder and the outer cylinder. The heating medium passage has an annular opening at one axial end side of the throttle body. Holes extending across the wall of the outer cylinder are formed so as to communicate with the heating medium passage. The annular opening of the heating medium passage is sealed by a sealing member at the one axial end side of the throttle body. Accordingly, even when the inner cylinder and the outer cylinder are made of a resin material, it becomes possible to transfer heat of the heating medium to the entire vicinity or surrounding of the throttle valve by supplying heating medium into the heating medium passage formed outside the inner cylinder.
Hence, the first aspect of the present invention provides a simplified arrangement capable of effectively avoiding the icing phenomenon of the throttle apparatus.
Furthermore, integrally forming the inner cylinder and the outer cylinder makes it possible to simplify the assembling steps of the throttle body compared with a manufacturing method of separately forming the inner cylinder and the outer cylinder. Thus, the manufacturing cost can be reduced correspondingly.
Furthermore, the first aspect of the present invention can employ the molding operation which uses extractable dies for forming the inner cylinder and the outer cylinder so as to leave the heating medium passage therebetween. No cutting operation is required for forming the heating medium passage. Thus, the first aspect of the present invention provides a throttle body arrangement capable of reducing manufacturing steps and easy to manufacture, thereby further reducing the manufacturing cost.
Furthermore, a second aspect of the present invention provides a second throttle body for an engine and a second manufacturing method for the engine throttle body. According to the second aspect of the present invention, an inner cylinder and an outer cylinder are formed integrally so that the outer cylinder is disposed outside the inner cylinder. A heating medium passage is formed between the inner cylinder and the outer cylinder. The heating medium passage has a first annular opening at one axial end side of the throttle body and a second annular opening at the other axial end side of the throttle body. Holes extending across the wall of the outer cylinder are formed so as to communicate with the heating medium passage. The first annular opening of the heating medium passage is sealed by a first sealing member at the one axial end side of the throttle body. The second annular opening of the heating medium passage is sealed by a second sealing member at the other axial end side of the throttle body. Accordingly, even when the inner cylinder and the outer cylinder are made of a resin material, it becomes possible to transfer heat of the heating medium to the entire vicinity or surrounding of the throttle valve by supplying heating medium into the heating medium passage formed outside the inner cylinder.
Hence, the second aspect of the present invention provides a simplified arrangement capable of effectively avoiding the icing phenomenon of the throttle apparatus. Furthermore, the icing phenomenon can be further effectively prevented when the heating medium passage is formed to communicate with the inlet side of a surge tank of an engine and with the outlet side of an air cleaner of the engine.
Furthermore, integrally forming the inner cylinder and the outer cylinder makes it possible to simplify the assembling steps of the throttle body compared with a manufacturing method of separately forming the inner cylinder and the outer cylinder. Thus, the manufacturing cost can be reduced correspondingly.
Furthermore, the second aspect of the present invention can employ the molding operation which uses extractable dies for forming the inner cylinder and the outer cylinder so as to leave the heating medium passage therebetween. No cutting operation is required for forming the heating medium passage. Thus, the second aspect of the present invention provides a throttle body arrangement capable of reducing manufacturing steps and easy to manufacture, thereby further reducing the manufacturing cost.
Furthermore, a third aspect of the present invention provides a third throttle body for an engine and a third manufacturing method for the engine throttle body. According to the third aspect of the present invention, a metallic core member is formed so as to integrally form an inner cylindrical portion and an outer cylindrical portion which are coaxially arranged. A heating medium passage is formed between the inner cylindrical portion and the outer cylindrical portion. The heating medium passage has an annular opening at one axial end side of the throttle body. Holes extending across the wall of the outer cylindrical portion and the wall of a housing are formed so as to communicate with the heating medium passage. The annular opening of the heating medium passage is sealed by a sealing member at the one axial end side of the throttle body. Accordingly, the inner cylindrical portion forming part of the metallic core member is made of a metallic member. Heat of the heating medium is effectively transferred to the entire vicinity or surrounding of the throttle valve. Using a resin housing for accommodating the core member is advantageous in that the housing serves as a heat insulating member which prevents heat from radiating out of the core member. Heat of the heating medium can be effectively transferred to the entire vicinity or surrounding of the valve member. Hence, the third aspect of the present invention provides a simplified arrangement capable of effectively avoiding the icing phenomenon of the throttle apparatus.
Furthermore, integrally forming the inner cylindrical portion and the outer cylindrical portion as a core member makes it possible to simplify the assembling steps of the throttle body compared with a manufacturing method of separately forming the inner cylinder and the outer cylinder. Thus, the manufacturing cost can be reduced correspondingly.
Furthermore, the third aspect of the present invention can employ the molding operation which uses extractable dies for forming the inner cylindrical portion and the outer cylindrical portion so as to leave the heating medium passage therebetween. No cutting operation is required for forming the heating medium passage. Thus, the third aspect of the present invention provides a throttle body arrangement capable of reducing manufacturing steps and easy to manufacture, thereby further reducing the manufacturing cost.
Furthermore, according to the throttle body for an engine of the present invention and the manufacturing method for the engine throttle body of the present invention, it is preferable that hot water of a cooling water passage of the engine flows into the heating medium passage. Heat of the engine cooling water can be surely transferred to the entire vicinity or surrounding of the valve member. Hence, the present invention provides a simplified arrangement capable of effectively avoiding the icing phenomenon of the throttle apparatus.
Another object of the present invention is to provide a throttle body capable of preventing leakage of heating fluid or comparable heating medium and surely heating an annular member by this heating fluid or comparable heating medium. Furthermore, another object of the present invention is to provide a throttle apparatus incorporating this throttle body.
To accomplish the above and other related objects, the present invention provides a fourth throttle body which comprises an annular member is attached to an inside wall of a resinous or resin-made main body defining an intake passage. The annular member has a heat conductivity higher than that of the main body. The annular member has a fluid passage entirely extending in the annular member. A fluid inlet and a fluid outlet of the fluid passage are opened on an outer wall of the annular member exposed to an outside of the main body. An appropriate piping is attached to the annular member so that fluid is supplied into the fluid inlet of the annular member and discharged from the fluid outlet. Thus, the fourth throttle body effectively prevents the heating fluid from leaking through the gap or clearance between the main body and the annular member. Furthermore, the fluid flowing in the fluid passage directly heats the annular member. Thus, the heat of the fluid can be effectively transferred to the annular member.
Furthermore, the present invention provides a fifth throttle body comprising an annular member attached to an inside wall of a resinous or resin-made main body defining an intake passage. The annular member has a heat conductivity higher than that of a resinous main body. A cover member is disposed outside the annular member so as to form a fluid passage interposed between the cover member and an outer wall of the annular member. A sealing member is provided for sealing a clearance between the cover member and the outer wall of the annular member. Thus, the fifth throttle body effectively prevents the heating fluid from leaking through the gap or clearance between the main body and the annular member. Furthermore, the fluid directly heats the outer wall of the annular member. Thus, the heat of the fluid can be effectively transferred to the annular member.